Just with regards to what Jazz said above - I don't believe it's actually legal to make your own number plate in the case of having a bike rack that covers it...It must be an ACT government issued plate (they make them for bike racks too)
However, good luck. I'd say you're likely buggered. As Sin said, it needs to comply with both A and B.
If I were you, I'd be happy with the $375 fine. I recently got done for no front number plate, however instead of a fine I received a defect advising I needed to take it to Dickson. I reported my front number plate stolen and surrendered my remaining plate; RTA didn't give a fark.
So far mine has/will cost me:
Initial inspection at Dickson ($55)
Braided brake lines ($160+fitting)
Borrow legal exhaust ($25+ depending on how long I need it)
ENGINEER'S CERTIFICATE ($1046)
Since it's been more than 1 calendar month from initial inspection, I need to pay full $55 for the next one....which the dream boats will undoubtedly fail me on.
Wanna swap your fine for a defect? lol